<!DOCTYPE html>
<html>
<head>
<style>
iframe {
  position: absolute;
  margin-left: 5vw;
  margin-top: 60vh;
  width: 90vw;
  height: 40vh;
  border: 0px;
}
div.bottom {
  position: absolute;
  top: 10000px;
  left: 0px;
  width: 1px;
  height: 1px;
}
p {
  position: fixed;
}
</style>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<script src="resources/large-sticky-ad-testharness.js"></script>
</head>
<body marginwidth="0" marginheight="0">
<!-- To trigger the first contentful paint at the very start -->
<p>some content</p>
<!-- To be positioned further down in the main page to make the page scrollable -->
<div class="bottom"></div>
<script>
promise_test(async function(t) {
  // Create the large-sticky-ad.
  appendAdFrameTo(document.body);

  let ad_candidate = document.getElementsByTagName("iframe")[0];
  let initial_margin_top = parseInt(window.getComputedStyle(ad_candidate).marginTop, 10);

  // After 1500ms, force a layout update so that the sticky ad detector is
  // aware of the sticky ad candidate.
  await timeout(1500);
  await forceLayoutUpdate();
  assert_false(internals.isUseCounted(document, kLargeStickyAd));

  // Scroll down to 5000px. Reset the frame's position w.r.t. the viewport
  // to its initial position.
  window.scrollTo(0, 5000);
  ad_candidate.style.marginTop = initial_margin_top + window.scrollY + 'px';

  // After 1500ms, force a layout update. At this point the scrolling
  // position has changed by a distance greater than the candidate's height,
  // so the use counter kLargeStickyAd should be recorded.
  await timeout(1500);
  await forceLayoutUpdate();
  assert_true(internals.isUseCounted(document, kLargeStickyAd));
}, "Test UseCounter for large-sticky-ad at the bottom when the frame itself has an absolute position, and along with scrolling the ad's position w.r.t. the browser viewport gets frequently reset to the initial postion.");
</script>
</body>
</html>
